1. Field of the Invention
The invention relates to an acetone-extracted product obtained from gamboge resin and compounds further purified from the acetone-extracted product, including a new compound called formoxanthone A. The acetone-extracted product and the further purified compounds have been demonstrated to have activities in inhibiting the growth of tumor/cancer cells. The invention also relates to processes for obtaining the further purified compounds, and uses of the acetone-extracted product and the further purified compounds in the preparation of pharmaceutical compositions for inhibiting the growth of tumor/cancer cells.
2. Description of the Related Art
Gamboge resin is the gamboge of Garcinia sp. secreted by the plant Garcinia of the family Guttiferae. It has been used as a source of vegetative dyes and pigments since the old days. It is also used in folk medicine in some areas such as India and Thailand.
Garcinia (TENGHUANG in pinyin), which is commonly known as gamboge, is a kind of evergreen trees that grow in tropical regions. The main species grown in India is Garcinia morella Desv, whereas the main species grown in Thailand is G. harburyi Hook. Before the flowering-period, the bark of the tree is cut open in a spiral shape about 2 meters from the ground to collect the exuding resin. The resin is then subjected to heat-drying to result in a solidified gamboge resin.
According to traditional Chinese medicine (TCM), gamboge is effective in combating inflammations, clearing away toxins, stopping blood bleeding, and killing worms. Ever since 1934, there have been a number of reports on the components of the gamboge resin. At present, it is known that many compounds can be isolated from extracts of gamboge resin, including: morellin, morellic acid, gambogic acid, morellinol, isomorellin, isomorellic acid, isogambogic acid, isomorellinol, neogambogic acid, desoxymorellin, dihydroisomorellin, α-guttiferin, and β-guttiferin, etc.
Some studies have reported the cytotoxic activity of certain components of gamboge resin on human lung cancer cells (HEL cells), human cervical cancer cells (HeLa cells), and human nasopharyngeal cancer cells (KB cells) [M. Tada et al. (1996), Phytochemistry, 41, 815–920; G. A. Cordell et al. (1993), Magnetic Resonance in Chemistry, 31, 340–347].
It is pointed out in a report that the roots of Anemone raddeana are used in Chinese folk medicine to cure rheumatism and neuralgia, and that betulin and betulinic acid can be isolated from ethanol extracts of the roots of Anemone raddeana. Betulin has been proven to be capable of preventing tyrosyl phosphorylation of proteins in human neutrophils, thereby suppressing superoxide generation [K. Yamashita et al. (2002), Clinica Chimica Acta, 325, 91–96].
In a report by Darrick S. H. L. Kim et al. in Bioorganic & Medicinal Chemistry Letters (1998), 8, 1707–1712, it has been demonstrated that simple modifications of the parent structure of betulinic acid can produce derivatives that can be developed as potent anticancer drugs. There are reports which point out that betulinic acid can trigger apoptosis by a direct effect on mitochondria [Simone Fulda et al. (1998), The Journal Of Biological Chemistry, 278, 33942–33948], and has selective cytotoxicity on tumor cells [Valentina Zuco et al. (2002), Cancer Letters, 175, 17–25].
To the applicants' knowledge, there has not been any report or patent that discloses the isolation of betulin and betulinic acid from gamboge resin.
U.S. Pat. No. 6,462,041 has disclosed gambogic acid, its analogs and derivatives as represented by the following Formulae I, II and III:
wherein R1 to R5 are such as defined in the aforesaid patent.
Compounds having one of the aforesaid Formula I–III are disclosed to be activators of caspases and inducers of apoptosis.
EP 0 428 815 A1 discloses a process of purifying a cytolytic toxin from the resin of Garcinia morella Desv, which relates to a product identified by the name GMD1630 that is obtained by ethanol extraction, chloroform extraction, and thin layer chromatography (TLC). However, the patent does not disclose whether the GMD1630 product is a single compound or a mixture of compounds with similar properties.
In view of the foregoing, the preparation of bioactive extracts or purified compounds from gamboge resin for the manufacture of drugs, such as anticancer drugs, should merit further study and research.